Convert hp to watts

One horsepower equals 745.699872 watts. To convert any number of horsepower to watts, multiply by 745.69987158.

The converter above works in both directions and updates as you type. Below you will find the formula, a worked example and a reference table of common values.

Power is energy per unit time, and the conversions here are all between ways of expressing that rate. Watts and kilowatts are the SI forms; horsepower survives in engine ratings because James Watt coined it to sell steam engines against the animals they replaced. Confusing power with energy is the persistent error in this category: a wattage tells you nothing about consumption or cost until a duration is attached to it.

hp to watts formula

To go the other way, use horsepower = watt ÷ 745.69987158.

About these units

James Watt defined horsepower to market steam engines against the draught horses they replaced. Mechanical horsepower is about 745.7 watts.

The watt is one joule per second — a rate, not a quantity. An appliance’s wattage tells you nothing about its running cost until you say how long it runs.

Horsepower is also written bhp and brake horsepower. Watt is also written watts.

Sources

1. National Bureau of Standards, "Refinement of Values for the Yard and the Pound", Federal Register, 1 July 1959 — the international yard as exactly 0.9144 m and the avoirdupois pound as exactly 0.45359237 kg.
2. NIST Special Publication 811, Guide for the Use of the International System of Units (SI), 2008 edition — conversion factors for units outside the SI.